Field of the Invention
The invention relates to the field of inner conductors for a coaxial cable or to the field of coaxial cables for transmitting high-frequency signals.
Coaxial cables for transmitting signals with high frequencies are known from the prior art. These cables comprise an inner conductor which is surrounded by a dielectric and an outer conductor.
Rotary swaging machines, by means of which ductile materials can be deformed either continuously or intermittently, have been known from the prior art since the beginning of the last century. These rotary swaging machines generally comprise a forming tool consisting of two or four jaws arranged in pairs opposite one another. The jaws of the forming tool are for example deflected inwards in the radial direction by means of circumferential rollers. At the same time, said jaws move in the circumferential direction. The forming tool comprises a central, mostly continuous, working opening which has a tapering cross section in the longitudinal direction. Work pieces to be processed can be introduced into the working opening of the forming tool and removed via the same opening or, in the case of a continuous process, via a second opposite opening. The work piece is continuously deformed within the working opening by means of the jaws which move in the radial and circumferential direction. As a result of the movement of the jaws, the working opening has a variable cross section. Rotary swaging is used for example in the production of wire ropes or forged pieces in the motor industry. A number of fields of application for rotary swaging machines are known from the patent literature. A few selected examples will be briefly described below.
Discussion of Related Art
U.S. Pat. No. 6,641,444B2 from the Yazaki Corporation, granted on Nov. 4, 2003, describes a structure and a method for joining an electric cable and a cable end piece by means of rotary swaging. For this purpose, the insulation is first stripped at the cable end, so that the litz conductor is exposed. Said litz conductor is then slid into a hollow cylindrical sleeve. Next, the sleeve is compressed in the radial direction by means of rotary swaging. This compression compacts the litz conductor and thus reduces the electrical resistance.
U.S. Pat. No. 7,174,633B2 from the Yazaki Corporation, granted on Feb. 13, 2007, also describes a method for connecting an electric cable to a cable end piece. To do this, an electrically conductive adhesive (e.g. a paste made of epoxy and nickel powder) is filled into a tubular end of a cable end piece. Next, the litz conductor of the cable end, having been stripped beforehand, is inserted into the hole. The tubular cable end piece is then radially compressed by means of rotary swaging and brought into tight contact with the litz conductor. The nickel powder in the paste, as the conductive filler, should thereby destroy any possible oxide layers on the metal parts and increase the conductivity.
The Japanese publication JP7226118A2 from the Yazaki Corporation describes the use of a rotary swaging method to prevent uncontrolled deformation of a wire rope in a subsequent rolling process. The use of a wire rope which is stranded in multiple layers is provided. The rolling process serves for the reduction of the diameter and for the increase of the length of the wire rope, respectively.
The Japanese publication JP7249329A2 from the Yazaki Corporation describes the production of a compressed concentric multi-layer wire rope and an apparatus for the production thereof. In the described method, the rope is first stranded from a plurality of wires. Before being wound up, the cable is compressed radially and deformed by a rotary swaging tool.
The Japanese patent JP3257388B2 from the Yazaki Corporation describes the geometry of a plurality of different forming tools for compressing multi-layer stranded wire strands by means of rotary swaging. Since relative rotations between the wire rope and the rotary swaging tool may cause damage to the wire rope at least at high compression levels, the swaging jaws, when closed, do not form a circular cross section, but rather a cross section which is flattened at the jaw edges.
The German publication DE19835901A1 from River Seiko KK and Asahi Optical Co. Ltd. describes an endoscopic wire loop which is made of corrosion-resistant wire and can be used for example for the surgical removal of polyps using high-frequency electric current. According to DE'901, such loops are typically produced from stranded wires. A frequent feature of corresponding loops is a sharp U-shaped curvature at the distal end thereof, which is intended to improve the withdrawal of the loop back into the sleeve-shaped endoscopic guide instrument. In practice, however, the very small radius of curvature in the U-shaped part causes the wires of the strand to slacken and to be irregularly deformed, which leads to uncontrolled spreading of the wires. In the event of high mechanical stress or Joule heating, this can cause the tool to break down. The method used, as described in DE'901, is based on a forging process in which a stranded wire is guided through a forging die, the hole in which has a diameter which is (8-10.5%) smaller than that of the strand. This leads to radial compression of the strand. This causes the wires of the strand to be deformed and the gaps between the wires to disappear. The wires at the surface are thus given a trapezoidal cross section and the entire stranded wire is given a very smooth surface. The resultant stranded wire should maintain this smooth surface even in the case of a sharp curvature, and it is not fanned out into its wires, respectively. In addition, it is stated that the wire according to the invention “looks superior in quality” and that as a result a wire loop instrument produced therefrom has a high commercial value.
GB794411A from British Ropes Ltd. was published in 1958 and claims a method, and a means for the implementation thereof, for treating wire ropes such that its wires are given a cross section which deviates from the round shape owing to the influence of external radial forces. This method is characterised in by an axial bias of the rope, which bias is constantly active in the region of the radial pressure forces during deformation. Together with the radial force, this axial force leads to an increase in the length of the rope and the strands, respectively. The axial force is selected such that the wire material begins to yield. Radial forces can be exerted by means of a rotating tool.
U.S. Pat. No. 6,023,026 from the Nippon Cable Systems Inc. was published in 2000 and describes a new type of rotary swaged, forged steel rope, which has both high mechanical flexibility/suppleness and high tensile strength. These improved properties are the result of both an optimized composition of the individual rope lines as well as specified wire diameter ratios and a measure for the compression during the deformation process.
DE1943229 (or U.S. Pat. No. 3,651,243) from Western Electric Co. Inc. was first published in 1970 and relates to a coaxial cable comprising a stranded inner conductor. Undesired spikes in the return loss are reduced by varying the pitch during stranding.